1. Field of the Invention
This invention relates to article conveyors of the type having article carrying tubes moving in an endless path and pushers movable lengthwise of the tubes to divert articles off of the conveyor and, more particularly, to a control switch for crossing track sections that guide movement of the pushers.
2. Background Art
One conventional type of article conveying system utilizes a plurality of elongate tubes moving in an endless path transverse to the length of the tubes. An exemplary system is shown in U.S. Pat. No. 4,760,908, to Houghton. In such systems, the articles are carried on top of the tubes and diverted to selected stations by pushers moving lengthwise of the tubes as the conveyor is operated. Each pusher has a depending guide element which cooperates with a guide track system and is thereby progressively deflected lengthwise of the tube.
In some such systems, there are crossing track portions. This permits the articles to be pushed selectively off either side of the tubes over the same conveyor length. The crossing arrangement accounts for a significant savings in conveyor and thus warehouse space, however necessitates the incorporation of a switch to selectively guide the pushers to either one side or the other of the conveyor.
Heretofore, switches have been controlled by a combination of electronic and mechanical components. Typically, a photosensor will detect an article and in response thereto produce a signal that dictates the position of the switch.
The problem with the above type switch is that, while it may be relatively sophisticated, it is prone to failure. If for any reason there is a misread by the photosensor, the switch could be thrown into the wrong position which could result in misdirection of articles, jamming and potential damage to the system. Down time and improperly sorted articles are inconvenient and expensive to the user of the conveyor.